A horizontal type continuous casting machine has recently been developed and is being industrialized, principally for reducing construction costs, which comprises horizontally fitting a casting nozzle to the lower part of the side wall of a tundish; arranging a mold horizontally along the horizontal axial line of said casting nozzle, in close contact with the tip of said casting nozzle; casting a molten metal received in a tundish through the casting nozzle horizontally into the mold to form a cast strand; and, withdrawing the cast strand thus formed always horizontally from the exit of the mold in the form of a long strand while cooling said cast strand in a secondary cooling zone provided along a path of withdrawal of the cast strand.
One of the problems encountered when manufacturing a cast strand by means of the above-mentioned horizontal type continuous casting machine is that, when the cast strand withdrawn from the mold during operation is cooled in the secondary cooling zone, the shell of said cast strand is broken and the molten metal flows out, i.e., occurrence of a breakout. Occurrence of a breakout of a cast strand as mentioned above in the operation of a horizontal type continuous casting machine cannot be completely prevented at present.
In the horizontal type continuous casting machine, as mentioned above, the cast strand withdrawn from the mold is cooled by water ejected toward the cast strand in the secondary cooling zone provided along the path of withdrawal of cast strand from the exit of the mold. For the purpose of receiving the water having cooled the cast strand and of pouring said water into a tank, a water discharge channel is installed directly below a secondary cooling zone. When a breakout occurs to the cast strand, therefore, the molten metal flowing out from the cast strand flows downwardly to said water discharge channel, comes into contact with the water having cooled the cast strand, and may cause a steam explosion as a result.
It is empirically known that, in order to prevent a steam explosion caused by an occurrence of a breakout of the cast strand, it suffices to pour the outflowing molten metal into a large quantity of water, e.g. over eight times as large as the quantity of said molten metal in weight. For this purpose, however, it is necessary to install a large-capacity tank capable of containing from 7 to 10 tons of water directly below said secondary cooling zone. Installation of such a large-capacity tank directly below the secondary cooling zone leads to considerable difficulties in designing and constructing the secondary cooling zone, and therefore such installation requires huge installation costs.
Under such circumstances, there is a strong demand for the development of an apparatus for preventing a steam explosion, caused by molten metal breaking out from a cast strand, in the water discharge channel of the secondary cooling zone of the cast strand in a horizontal type continuous casting machine, but such an apparatus has not as yet been proposed.